启动报错：
The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received
No appropriate protocol (protocol is disabled or cipher suites are inappropriate)
The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server
The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
Exception in thread "main" com.mysql.cj.jdbc.exceptions.CommunicationsException: Communications link failure解决：
连接池
url的设置问题，加上：
?useUnicode=true
而且
useSSL=false 要设置成false